Joint analysis using ultrasound

ABSTRACT

A method is provided for generating at least one quantitative measure of a joint comprising sending an acoustic signal to at least a part of a joint, receiving said acoustic signal after modification by said joint, analyzing the received acoustic signal with a computer, and generating, from said computer, one or more of a quantitative surface, quantitative volumetric and quantitative measurements of the physical properties of the joint or a portion thereof.

FIELD OF THE INVENTION

[0001] The present invention relates to quantifyng joint measurementsusing ultrasound.

BACKGROUND OF INVENTION

[0002] Observation of joint structures with ultrasound, though describedin many articles in the past decades, has failed to become an acceptedjoint measurement tool. As early as 1983, ultrasound was suggested as ameans of observing joint cartilage. As an example, Alex M. Aisen, M Det. al. Radiology Vol. 153 Number 3, Dec. 1983, “Sonographic Evaluationof the Cartilage of the Knee,” demonstrates the use of ultrasound inobserving “changes in the surface characteristics and thickness ofcartilage”. This ultrasound method relies on subjectively evaluating anultrasound image.

[0003] Ultrasound has the potential to be useful in observing some jointstructures besides cartilage. According to Iagnocco, et al.Scand. JRheumatol Vol. 21: 201-203, 1992 in “Sonographic Evaluation of Femoralcondylar Cartilage in osteoarthritis and rheumatoid arthritis,”“Sonography of the knee makes it possible to study the anatomicaldetails of this articulation such as synovial membrane, intra-articularfluid, articular cartilage, ligaments and tendons, menisci, possiblepopliteal cysts, their dimensions and location.” Again, this ultrasoundmethod relies on subjective evaluation of an ultrasound image.

[0004] Allessandro Castriota-Scanderbeg et al., in “Skeletal ageassessment in children and young adults: Comparison between a newlydeveloped sonographic method and conventional methods,” SkeletalRadiology 1998 27:271-277, propose a method for assessing skeletal ageusing ultrasound imaging measurements of the thickness of femoral headarticular cartilage.

[0005] Ultrasound can also provide important information about horsejoint conditions that is important to their trainers, as stated byTomlinson BVSc., et. al., Veterinary Radiology and Ultrasound Vol. 41no. 5, 2000 pp. 457-460 “Ultrasonographic evaluation of TarsocruralJoint Cartilage in Normal Adult Horses,” “Diagnostic ultrasound hasproven to be more sensitive than radiology for the early identificationof periarticular remodeling and osteophyte formation” in evaluatingequine Osteoarthritis. Again, this method relies on subjectiveevaluation of an overall ultrasound image.

[0006] Ultrasound observation of joint structures is advantageousbecause its probes can be applied external to the body so it can be usedin a non-sterile environment. Ultrasound provides joint inspectionwithout using ionizing radiation as does X-ray, allowing examinations tobe repeated frequently without risk to the patient. Ultrasound does notrequire a special media, such as an X-ray plate, with which to gatherdata and can provide better resolution than X-ray, particularly of thecartilage and soft tissue structures. Also, ultrasound is a lessexpensive imaging unit than X-ray, CT or MRI. For these reasons,ultrasound is useful for imaging in a doctor's office, mobile clinics,theater of battle or in screening programs in undeveloped countries.

[0007] Yet, for all its advantages, ultrasound has not lived up to itspotential. As noted by Walter Grassi et al., June 1999 Seminars inArthritis and Rheumatism vol. 29, No. 6. “Sonographic Imaging of Normaland Osteoarthritic Cartilage,” as of mid-1999, ultrasound potential “isstill under investigation.”

[0008] Ultrasound has apparently not gained widespread use for assessingjoints beyond imaging, in spite of its apparent suitability.

OVERVIEW OF JOINT STRUCTURES

[0009] Joints are connections, typically movable, between two or morebones and include many structures that lend themselves to quantitativemeasurement. Such structures include, but are not limited to cartilage,chondrocytes, subchondral bone, joint capsule, joint fluid, ligamentsand tendons:

[0010] (a) Cartilage is a tissue that consists of cells calledchondrocytes in an extracellular matrix. The cartilage coats the ends ofbones within a joint. Cartilage acts as a shock absorber against impactto the ends of bone during actions such as walking, running or jumping.The surface of cartilage provides an almost friction-free surfacebetween bones as they move against each other.

[0011] (b) Chondrocytes are cells that lay down new cartilage.Chondrocytes produce and maintain the extracellular matrix.

[0012] (c) Subchondral bone, is a part of the bone that is locateddirectly below cartilage and demonstrates changes in a variety of statesthat affect a joint.

[0013] (d) Joint fluid is a complex liquid that serves to nourish thecartilage, lubricate the tissue of a joint and carry waste away fromcartilage.

[0014] (e) Joint capsule is a flexible tissue joint covering that givesa joint support and seals in the joint fluid that lubricates the jointstructures. Its inner lining is the synovial membrane that produces andreplenishes joint fluid.

[0015] (f) Ligaments are fibrous bands that connect one bone to another,usually within or part of a joint capsule.

[0016] (g) Tendons are the fibrous ends of a muscle that attaches it tobone and can be incorporated into joint structures.

SUMMARY OF THE INVENTION

[0017] An aspect of some embodiments of the invention relates toacquiring quantitative measures of joint properties, in particular,surface, physical and volumetric measures.

[0018] As used herein the term quantitative surface measure means avalue that characterizes a property of a two dimensional surfacemeasurement of at least a part of a joint structure, such as the amountof surface area affected by osteoarthritis-related pitting.

[0019] As used herein the term physical measure means a value thatcharacterizes a property of internal volume of at least a part of ajoint structure, such as cartilage. Exemplary physical measures includespeed of sound, density of osteophytes and cross-sectional brightness.

[0020] As used herein the term volumetric measure means a value thatcharacterizes the volume of at least a part of a joint structure, suchas cartilage. An exemplary volumetric measure is the volume of an areaof joint cartilage that has been affected by thinning and/or pitting dueto osteoarthritis.

[0021] Being quantitative, rather than qualitative, such measures can beused, for example, to indicate a joint state directly, for example, inquantifying the quality of cartilage. In some exemplary embodiments ofthe invention, measures are generated on the basis of average, relativeor other statistical properties and/or on the basis of absolutemeasurements of a joint.

[0022] In an exemplary embodiment of the present invention, quantitativeultrasound joint measurements are acquired during performance ofdifferent activities, for example during walking or running.

[0023] In an exemplary embodiment of the present invention, quantitativeultrasound joint measures are compiled into a database that associates aqualitative meaning or a state identification with raw measurement data.Such a database, for example, correlates ultrasound measurements withage, weight, occupation sex, ethnic group and/or related disease state.

[0024] An aspect of some embodiments of the invention relates toestablishing quantitative joint properties of two or more regions of ajoint structure. In one example, a quantitative comparison is madebetween the degree of pitting in two or more regions of cartilage. Anexemplary use of such quantitative information is in locating optimalcartilage graft donor sites and optimal cartilage graft recipient sitesin autogenous cartilage reconstruction.

[0025] An aspect of some embodiments of the invention is correlation ofquantitative ultrasound joint measures with disease states.Osteoarthritis, for example, is a disease that results from overuseand/or improper use of a joint and often becomes manifest after repeatedinflammation of a joint. In osteoarthritis, joint structures, such ascartilage, bone, subchondral bone, and soft tissue, can bequantitatively measured to provide an indication of disease. Suchindication may lead, possibly in conjunction with other measures, todiagnosis and/or provide an indication for ongoing treatment regimen.

[0026] Additionally or alternatively, quantitative ultrasound jointmeasurements are correlated with disease state progression in geneticjoint disease, such as in sarcoid. Optionally, quantitative measurementsare used to track disease progression during treatment.

[0027] Additionally or alternatively, quantitative measures arecorrelated with other physiologic measurements, for example, blood valuemeasurements. In an exemplary embodiment blood uric acid levels arecorrelated with joint cysts containing uric acid in hyperuricemia

[0028] There is thus provided, in accordance with an embodiment of theinvention, a method for generating at least one quantitative measure ofa joint comprising

[0029] sending an acoustic signal to at least a part of a joint;

[0030] receiving said acoustic signal after modification by said joint;

[0031] analyzing the received acoustic signal with a computer; and

[0032] generating, from said computer, one or more of a quantitativesurface, quantitative volumetric and quantitative measurements of thephysical properties of the joint or a portion thereof.

[0033] In an embodiment of the invention, generating a quantitativemeasure comprises generating a value of a quantitative surface measure.

[0034] Optionally, generating a value of a surface quantitative measurecomprises establishing a region of interest within a pixel imagegenerated from said received acoustic signal and measuring thebrightness of pixels within said region of interest.

[0035] Optionally, generating a value of a surface quantitative measurecomprises establishing a region of interest within a pixel imagegenerated from said received acoustic signal and averaging thebrightness of pixels within said region of interest. Optionally, theregion of interest is a line. Optionally, the region of interest isdetermined manually by an operator. Optionally, the method includes acomputer automatically determining a region of interest.

[0036] In an embodiment of the invention, generating comprisesgenerating a value of a quantitative volumetric measure from saidacoustic signal. Optionally, the volumetric value comprises the amountor volume of one or more of pitting in cartilage, bone cysts, jointfluid, osteophytes.

[0037] In an embodiment of the invention, said generating is aquantitative physical measure from said acoustic signal. Optionally,said physical measure from said acoustic signal comprises one or more ofacoustic velocity, acoustic backscatter or acoustic attenuation.

[0038] Optionally, receiving the acoustic signal comprises generating apixel image from said joint.

[0039] Optionally, analyzing the received acoustic signal comprisesestablishing a region of interest within a pixel image generated fromsaid received acoustic signal.

[0040] Optionally, the quantitative measure comprises two or moremeasurements. Optionally, the quantitative measure comprises two or moremeasurements taken at separate times. Optionally, the quantitativemeasure comprises two or more measurements taken from separate areas ofsaid joint.

[0041] Optionally, the method includes comparing two or moremeasurements to each other.

[0042] Optionally, said quantitative measure comprises one or both of anecho method and through method.

[0043] Optionally said received acoustic signal comprises a global jointmeasure.

[0044] In an embodiment of the invention, the method includes activatingthe joint in conjunction with said sending and receiving. Optionally,said sending and receiving is performed during said activation.Optionally, sending and receiving is performed following saidactivation. Optionally, sending and receiving is performed prior to saidactivation.

[0045] In an embodiment of the invention, the method includes repeatingsaid receiving, analyzing and generating values, for at least twodifferent regions of said joint. Optionally, the method includesarranging said values for at least two different regions into a spatialmap. Optionally, the method includes combining said values for at leasttwo different regions into a qualitative descriptor.

[0046] In an embodiment of the invention, the method includes repeatingsaid receiving, analyzing and generating values at least two differenttimes for substantially the same measurement.

[0047] In an embodiment of the invention, the quantitative measureprovides a measure of cartilage.

[0048] In an embodiment of the invention, the quantitative measureprovides a measure of joint structures of one or more of synovialmembrane, joint fluid, joint capsule, a ligament, a bone, a tendon andan osteophyte.

[0049] In an embodiment of the invention, the joint comprises one ormore of a hip joint, a knee joint, an ankle joint, a tarsal joint, ametatarsal joint, a phalanx joint, a shoulder joint, an elbow joint anda wrist joint.

[0050] In an embodiment of the invention, the joint comprises at leastone of a syndesmosis, a synchondrosis, a diarthrodial joint, asynostosis.

[0051] In an embodiment of the invention, the joint is an equine joint.Optionally, the joint is at least one of, an equine intertarsal joint,an equine tarso-metatarsal joint, and an equine metatarsal joint.

[0052] In an embodiment of the invention, the joint is a human joint.

[0053] Optionally, the acoustic signal is received from a receiverlocated outside of said joint. Optionally, the acoustic signal isreceived from a receiver located inside of said joint. Optionally, thesignal is transmitted from a transmitter located inside of said joint.Optionally, the signal is transmitted from a transmitter located outsideof said joint.

[0054] In an embodiment of the invention, said analyzing comprisesreceiving said acoustic signal from said joint, generating a pixel imagefrom said joint and averaging the brightness of pixels along at leastone line of pixels from said image. Optionally, generating comprisesgenerating a value based on said average. Optionally, the at least oneline comprises at least two lines. Optionally, the method comprisesdisplaying averages of the brightness of pixels along two or more linesin graph format. Optionally, the graph displays averages of pixelbrightness along two or more lines through one or more of a cartilageregion, a bone region; and a non-cartilage soft tissue region.Optionally, a quantitative value is generated based on the amplitude ofvalues of said averages of pixel brightness. Optionally, a quantitativevalue is generated based on the slope of said averages of pixelbrightness.

[0055] In an embodiment of the invention, the measurement is responsiveto a signal that passes through a joint structure.

[0056] In an embodiment of the invention, the measurement is responsiveto a signal that echoes from a joint structure.

[0057] Optionally, the ultrasound signal provides a measure of one of;speed of sound, broadband ultrasound attenuation and dispersion ofultrasound signal.

[0058] Optionally, the method includes arranging said values into aspatial map. Optionally, the method includes arranging said generatedvalues into a temporal map.

[0059] In an embodiment of the invention, the quantitative value iscorrelated with one or more qualitative descriptors based on one or morealternative joint measurement methods. Optionally, the method includescorrelating at least two of said values with one of an MRI image of saidjoint, an X-ray CT or a nuclear scan image of said joint to provide aqualitative measure.

[0060] There is further provided, in accordance with an embodiment ofthe invention, a method of comparing at least one quantitativemeasurement to at least one qualitative descriptor, comprising:

[0061] acquiring one or more quantitative measurements from at least onejoint;

[0062] correlating, using a computer, said one or more quantitativemeasurements with one or more qualitative descriptors; and

[0063] generating a qualitative descriptor based upon said correlation.

[0064] In an embodiment of the invention, the one or more quantatativemeasurement s include measurements of cartilage.

[0065] Optionally, the qualitative descriptor comprises a clinical indexof said joint.

[0066] Optionally, the qualitative descriptor comprises joint measuresfrom one or more of an X-ray, an MRI image, an X-ray CT or a nuclearscan image.

[0067] Optionally, correlating comprises using a formula.

[0068] Optionally, correlating comprises using a formula with one ormore of the slope of the cartilage-soft tissue margin, the slope of thecartilage-bone margin, the minimum of the cartilage brightness and themaximum of the bone brightness as it appears in a cross sectionalbrightness graph of ultrasound data,as parameters.

[0069] Optionally, the method includes associating one or more personalparameters with said one or more values in said database. Optionally,the personal parameters comprise one or more more of age, sex, ethnicgroup, sport preference, activity level, occupation, geographic locationand nationality. Optionally, the personal parameters comprise one ofjoint disease symptoms, genetic joint disease inheritance, familialsystemic disease, blood values, infectious disease information, traumahistory and presentation. Optionally, the personal parameters compriseone or more clinical conditions. Optionally, the personal parameterscomprise one or more of pediatric trauma history, age, diet, and extentof joint damage.

[0070] Optionally, the one or more clinical conditions comprise one ormore of osteoarthritis, rheumatoid arthritis, hyperuricemia, and anautoimmune disorder and trauma.

[0071] In an embodiment of the invention, the method includes acquiringone or more quantitative measures of at least one joint;

[0072] correlating said one or more quantitative measures with aqualitative measure;

[0073] storing said one or more quantitative measures in said database;and

[0074] retrieving said one or more quantitative measure from saiddatabase.

[0075] Optionally, the one or more quantitative measures is correlatedwith a qualitative measure using a neural network.

BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Exemplary embodiments of the invention are described in thefollowing description, read with reference to the figures attachedhereto. In the figures, identical and similar structures, elements orparts thereof that appear in more than one figure are generally labeledwith the same or similar references in the figures in which they appear.Dimensions of components and features shown in the figures are chosenprimarily for convenience and clarity of presentation and are notnecessarily to scale. The attached figures are:

[0077]FIG. 1 illustrates quantitative ultrasound measurements of a jointin accordance with an embodiment of the present invention;

[0078]FIG. 2 schematically illustrates a portion of an ultrasound imageof a joint for analysis in accordance with an embodiment of the presentinvention.

[0079]FIG. 3 demonstrates a quantitative graph obtained from ultrasoundmeasurements of a joint;

[0080]FIG. 4 illustrates quantitative measurement of cartilage inaccordance with an embodiment of the invention;

[0081]FIG. 5A is an illustration of a joint reference grid forquantitative measurements in accordance with an embodiment of theinvention;

[0082]FIG. 5B is an illustration of a table of quantitative measurementsin accordance with an embodiment of the invention;

[0083]FIG. 5C is an illustration of a key for reference of values inaccordance with an embodiment of the invention;

[0084]FIG. 6 illustrates anatomy for describing quantitative ultrasoundmeasurement of a plurality of different joint structures in accordancewith an embodiment of the invention;

[0085]FIG. 7 illustrates anatomy for describing ultrasound measurementsof a damaged pediatric joint in accordance with an embodiment of theinvention;

[0086]FIG. 8A illustrates anatomy for describing ultrasound measurementsof an equine talocrural joint, shown in a caudal view, in accordancewith an embodiment of the invention;

[0087]FIG. 8B illustrates anatomy for describing ultrasound measurementsof an equine talocrural joint, shown in a cranial view, in accordancewith an embodiment of the invention; and

[0088]FIG. 9 is a block diagram of a computational system used inquantification of joint structure measurements in accordance with anembodiment of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS Overview of Osteoarthritis

[0089]FIG. 1 illustrates anatomy for the purpose of making quantitativemeasurements of joint, for example, to indicate or aid in diagnosis ofand/or track osteoarthritis (OA). OA is a major cause of pain in jointssuch as joint 100. Bones, such as a tibia 108 and a femur 102, in ahealthy joint, fit closely together. End of femur 102 is coated with anarea of cartilage 104 and end of tibia 108 is coated with an area ofcartilage 116 that provide a cushion during motion.

[0090] In the early stages of OA, in addition to inflammation andswelling of joint capsule 106, a plurality of focal blisters 144 mayform, such as in cartilage surface 104 of femur 106. As OA progresses,thinning occurs in a cartilage surface, such as cartilage surface 116 oftibia 108. An area of eburnation 140 can occur in cartilage surface 116,where cartilage 116 is completely worn away to expose bone 108.Cartilage 116 does not have its own blood supply so damaged cartilage116 does not heal well and damage to cartilage is often permanent.

[0091] With progression of OA, an osteophyte 142 may break off bone 108and/or cartilage 116 into joint fluid 114. Osteophyte 142 causes furtherdamage to cartilage 116 and joint capsule 106 and makes movement ofjoint 100 difficult. Untreated, OA progresses until joint 100 becomespermanently painful and stiff to move. On X-ray, late stage OA ischaracterized by a thin space between bones 108 and 102 of joint 100,signifying overall thinning of the joint cartilage with possibleappearance of osteophytes such as osteophyte 142.

[0092] As cartilage is not shown clearly on X-ray and often hidden bybone, early stages of OA are often not appreciated on X-ray, let alonegraded or quantified. Yet early detection and quantification of OA areimportant as palliative measures can be taken to prevent progression ofthe condition and possibly allow early-stage cartilage damage to heal.Treatment of OA often consists of non steroidal anti-inflammatory drugs(NSAID's), taping the joint and bracing the joint to preventinappropriate movement and relieve pressure during movement. Suchtherapy is often supplemented with physical therapy modalities such astherapeutic ultrasound and exercises. In equine OA, changes in trainingregimen are often necessary.

[0093] To ease joint inflammation, injections of steroidalanti-inflammatory drugs can be given. In lower extremity imbalance,orthotic shoe inserts, can be helpful. Using ultrasound in diagnosingand tracking OA removes the necessity of repeatedly using imaging withionizing radiation, so the disease progress can be tracked without riskto the patient and can provide a more precise picture of OA progress.

Introduction to Joint Imaging Quantitative Measurement

[0094] An ultrasound measurement of a joint 100 uses a probe 134 thatboth emits and receives an ultrasound beam 136, which strikes a targettissue such as tissue near a bone 102, and returns to probe 134 withinformation regarding the tissue.

[0095] In an exemplary embodiment of the invention, probe 134 is movedin a direction 138, while touching an area of skin 112, so that it canserially image various joint structures.

[0096] In an exemplary embodiment of the invention, probe 134, operateswith a frequency of between 5 MHz to 25 MHz. While this range ispreferred, probe 134 operates, in some embodiments, with a frequency of100 kHz or lower to 100 MHz or higher. As an example, a frequency of 8MHz typically provides a resolution of 0.2 millimeters. A higherfrequency such as 15 MHz typically provides a higher resolution, but hasless penetration of tissue. In an exemplary embodiment of the invention,probe 134 is used in the imaging method to construct and image or animage is reconstructed from multiple measurements (e.g., for one-, two-or three-dimensional imaging). Alternatively or additionally, a onedimensional or two dimensional phased array or mechanically scannedultrasound probes may be used to scan a volume.

[0097] In an embodiment of the invention, when producing an image of theknee, the patent's knee is bent by approximately 100 degrees (a somewhatsmaller bend is illustrated in FIG. 1). The ultrasound probe may belocated above the patella. Thus, the cartilage of the femur can beimaged.

An Ultrasound Image

[0098]FIG. 2 schematically illustrates an ultrasound image 200 of jointstructures such as bone 102, cartilage 104 and joint capsule 106 ofjoint 100, that is produced by probe 134. These structures are, for thepurposes of this discussion, healthy structures, with exception of focalblisters 144 in cartilage surface 104 (References are to FIG. 1).

[0099] In image 200 of joint 100 structures, a portion of cartilage 204is shown corresponding to area 104 in FIG. 1 and appears as a dark,curved band 204 with a margin 210 that separates it from a bone portion202 corresponding to bone area 102 in FIG. 1 and another margin 220 thatseparates it from a soft tissue portion 206 corresponding to soft tissueare 104 in FIG. 1. In contrast to line 210 that has a width, margin 220generally has no width, it is just the border between the soft tissueand the cartilage. When the entire portion of cartilage 204 is dark, itis referred to as being “hypoechoic,” in that there is less “echo,”represented than is represented by a lighter color. In cases where thecartilage is mildly worn, as in this example, there are a few portionsof white dots referred to as “speckles” 226 within cartilage 204. Thisindicates that the cartilage is suboptimal in this portion, caused by,for example, focal cartilage blisters 144 (in FIG. 1) and represent anearly stage of OA.

[0100] Alternatively or additionally, margin 210 may be less sharp,indicating that the cartilage is worn. When evidence of focalfibrillation is accompanied by a margin 210 that is not sharp, moresevere osteoarthritis may be present.

[0101] Alternatively or additionally, the linear thickness of astructure is measured. In an exemplary embodiment, cartilage 204 ismeasured for average thickness by taking the average value of uppercartilage margin 220 and subtracting the average value of lowercartilage margin 210. Thin cartilage is often indicative of more severeosteoarthritic changes.

Cross Sectional Brightness Measurements

[0102] Quantitative characterization using measurements of ultrasoundimage 200 may be obtained in accordance with an embodiment of theinvention. using one or more of several quantitative surface orvolumetric measurement methods, such as “Cross Sectional Brightness”(CSB). In the cross sectional brightness method, a line is definedmanually or automatically or semi-automatically parallel tobone-cartilage margin 210 and the brightness of each pixel along thisline is recorded. A single number representing the average brightness ofthese pixels is calculated.

[0103] Taking the average brightness of a line of pixels is repeated fora plurality of lines parallel to line 210 throughout ultrasound image200. As an example, 30 lines of pixels are acquired from bone portion202, 15 lines of pixels from cartilage portion 204 and 30 lines ofpixels from soft tissue portion 206. In this example, the lines areequally spaced with the number of lines determined by the tissue'sthickness on the ultrasound image. Based upon the quantitativemeasurement requirements, fewer or more lines of pixels can be definedand averaged. For instance, as few as one line can be measured in asingle tissue portion, or as many as 100 lines or more can be measuredin each tissue portion. Further, the width of each line can vary fromone pixel to several pixels (e.g., 30 pixels or more).

[0104] The brightness levels are taken from the digital file of theimage. They are the values of the color that are given to each pixel.(pixel=picture element). In cases of gray level images the values of thecolors usually range between 0=black to 255=white. In cases of coloredimages Red Green and Blue have values of 0 to 255. Brightness levels canthen be defined as the value of one of the Red Green or Blue values orthe value of the root of the sum of squares of the RGB values divided bythe square root of 3.

[0105] Alternatively or additionally, lines of pixels may be taken thatare not parallel to margin 210. The position of such lines, forinstance, could be based upon joint structure. For instance, a Region OfInterest (ROI) may be defined that encircles a specific portion of ajoint. In an exemplary embodiment, a region of interest is planar, andthe pixel pattern traces structures that lie on the same planarelevation. Alternatively, pixels may encircle a specific lesion, such asan area of focal cartilage thinning in osteoarthritis, with parallelpixel encirclement lines placed at regularly increasing or decreasingmean radii to provide a 3D surface map of an area

[0106] Alternatively or additionally, the distance between lines can beless than one pixel in size, for example, using a one-dimensionalimaging probe with electronic horizontal scanning having a displacementsmaller than the width of a beam. Alternatively or additionally, pixelsof different shapes may be used in order to image the joint for specificquantitative measurements, for example, rectangular versus squarepixels.

Graphing Quantitative Measurements

[0107]FIG. 3 is a representative graph 300 of average cross sectionalbrightness values for the lines measured in ultrasound image 200. An xaxis 314 represents the sequential number of each line of averagedpixels. A y axis 316 represents the average value of brightnesscalculated for each line. A soft tissue portion 306 represents crosssectional brightness measurement of an portion of soft tissue 206. Acartilage portion 304 represents cross sectional brightness measurementof a portion of cartilage 204. A bone portion 302 represents crosssectional brightness measurement of the whitish edge of the bone 210.Graph 300 demonstrates a joint with a cartilage portion 304 that is darkor “hypoechoic” except for an portion of slight elevation 326,corresponding to a lighter portion due to speckles 226 in cartilage 204.This is because the average cross sectional brightness of the linespassing through speckles 226 is brighter than the surrounding cartilage.

[0108] In an exemplary embodiment of the invention, graph 300 of CrossSectional Brightness, is used to ascertain the health of jointstructures. Optionally, in cartilage portion 304, a focal brightness 326is ascertained and correlated with its position within cartilage 102. Iffocal brightness 326 is a large portion and/or greatly elevated,osteoarthritic damage to cartilage may be present.

[0109] A sloped portion 320 occurs between soft tissue portion 306 andcartilage portion 304, defined by a line 332, signifying a rapidtransition between cartilage portion 304 and soft tissue portion 306.Such a slope indicates healthy structures such as smooth cartilage atthe cartilage-to-soft tissue junction, with adequate thickness ofcartilage and soft tissue, and/or intact and non-inflamed soft tissue. Aflatter slope and/or a jagged graph in portion 320, can signify thatosteoarthritis symptoms are present, such as joint inflammation, damagedsoft-tissue-to-cartilage junction and/or cartilage damage. Thebrightness of the graph of bone margin 302, signifies good structure anda lack of defects such as bone cysts.

[0110] In an exemplary embodiment, three parameters, the signal frombone 302, signal from cartilage 304 and slope 332 of softtissue-cartilage, provide important information to the caregiver aboutthe progression of osteoarthritis.

[0111] Alternatively or additionally, the values from portions of graph300 can be averaged to give a single value for each structure. As anexample, the graph line in portion 302 averages out to 67, signifyinggood bone, the graph line in portion 304 averages out to 39, signifyinggood cartilage structure health and the slope of graph line 332 is minus2, signifying good cartilage structure and health. When, for example,average cartilage brightness is increased, slope of graph line 332 isflatter, and average bone margin, portion 302, brightness is decreased,a joint disease, such as osteoarthritis, is indicated.

[0112] Additionally or alternatively, in the presence of pathology thatrequires further examination, another portion of graph 300 is analyzed.For instance, portion between bone 302 and cartilage 304 is smooth andhas slope along a line 312. A flatter slope and/or a jagged portion 310,signifies pathology at the bone-to-cartilage interface. When onlyportion 320 indicates abnormality, it is likely that the pathology isless severe. When both portions 320 and 310 show abnormality thepathology is more severe, such as severe Osteoarthritis.

[0113] With the appearance of larger elevation or greater brightness inportion 326, for example, a specific region of interest on image 200 canbe computed and analyzed to aid in diagnosis. Such a region of interestcan be defined by the physician upon viewing the image or automaticallyby an image processing software and a control unit that are discussedbelow. This only defines one coordinate of the damage. The physician maythen indicate the ROI manually on the image, based on the coordinategiven or an additional image processing algorithm can be used to locatethe ROI. For example, automatic determination of coordinate of a regionof interest may utilize a template of normal ultrasound values againstwhich the acquired information is compared with variations in valuesdefining a new region of interest. Additionally or alternatively,different measurements can be called for, either by the physician orautomatically with alternative data collection methods, such as changingthe probe, the type of probe, the number of probes and/or analysis ofthe collected data.

Alternative Data Analysis Methods

[0114] Alternatively or additionally to the cross sectional brightnessmethod, other methods of data analysis may be used to measure a jointand/or suggest or confirm a diagnosis. Two exemplary additional methodsfor examination of cartilage are Haralick's method and Histogram method.

Haralick's Analysis Method

[0115] In an exemplary embodiment of the invention, an analysis oftexture is performed using Haralick's image analysis method as isdescribed in Haralick, R. et al., “Textural features of imageclassification”, IEEE Trans. Syst. Man. Cyber. Vol 6:610-621, 1973, andVince, D. G. “Comparison of texture analysis methods for thecharacterization of coronary plaques in intravascular ultrasoundimages”. This method can be applied to a specific region of interest,for example, delineated on cartilage 204.

[0116] With Haralick's method, a co-occurrence matrix is calculated andparameters such as entropy, uniformity, element difference moment oforder 1 and 2 and inverse element difference moment of order 1 and 2,can be determined. (Gonzalez R. C. and Richard E. W., “Digital imageprocessing”, Addison-Wesley Publishing Company, New York, 1992, and JainA. K., “Fundamentals of Digital Image Processing”, Prentice Hall,Englewood Cliffs, N.J., 1989).

[0117] Alternatively or additionally, other measurements, such as theintensity of the cartilage signal, size of spots, arrangements of spots,and/or other texture analysis methods may be used. This is repeated atseveral locations, perhaps as few as two locations or as many as 100 or1000 locations. These measurements define the cartilage texture and/orstructure that can be correlated with information from a database fromwhich a qualitative assessment can be formulated as described below.

Histogram Analysis Method

[0118] In an exemplary embodiment of the present invention measures ofgray level Histogram are acquired. In this example, a region of interestis defined manually by the physician or automatically by imageprocessing software. Such a region of interest may, for example, belimited to a partial area of the cartilage, an area that encompasses aspecific defect or even a single measurement of entire cartilage surface116 (or 204 as it is shown in the ultrasound graph illustration). Theultrasound data is computed to find a gray level histogram, which showsthe distribution of pixel values and moments of the gray level histogramare computed. (Gonzalez R. C. and Richard E. W., “Digital imageprocessing”, Addison-Wesley Publishing Company, New York, 1992) Forexample one can calculate the first four moments, mean, SD, skewness andkurtosis. Other statistical parameters such as 3rd quantile or interquantile range of the gray level histogram can also be calculated. Thesemeasures can be used for grading. In general, they are believed tocorrelate with the “golden standards” used in the field.

Grading Cartilage Using A Combination of Parameters

[0119] A combination of parameters, such as from those noted above, mayprovide more insightful quantitative data on the state of cartilage.Alternatively or additionally, specific combinations can be deduced fromstatistical methods that compare the parameters obtained using theultrasound image and a grading parameter obtained by a “golden standard”such as MRI (H. K Gahunia, P. Babyn, C. Lemaire, M. J. Kessler, K. P. H.Pritzker, “Osteoartbritis staging: comparison between magnetic resonanceimaging, gross pathology and histopathology in the rhesus macaque”,Osteoarthritis and Cartilage, vol. 3, 169-180, 1995.) For example thefollowing exemplary equation results in a grading of the cartilagequality through comparison to other grading measures.

Grading=−1.6+1.0*CST+0.2*CB−0.05 4*BB  [Eq. 1]

[0120] where CST (cartilage soft tissue) is the slope of thecartilage-soft tissue margin, CB (cartilage brightness) is the minimumcartilage brightness and BB (bone brightness) is the maximum bonebrightness as they appear in cross sectional brightness graph 300. Thisgrading is based on a grading of a physician from ultrasound images.Other bases can, of course, also be used to generate grading formulas.

[0121] It should be understood that the above measurements (as well assome of the other quantitative measurements described in thisapplication) are somewhat dependent on the ultrasound device used aswell as on the settings of the device and, to some extent, on theoverlying structures in the particular patient. Furthermore, calibrationof the image brightness values should be performed prior to the crosssectional brightness calculation. This calibration can be performed byobtaining an image of a known phantom. The value of the brightness of apart of the phantom is then divided to an originally obtained brightnessof the same part. The results gives a value by which all of the newimages brightness values should be divided. For reference, the above andfollowing values are based on measurements made with a “synergy B”scanner of GE_Diasonics, utilizing a linear array probe (11/MI/33/LA).The probe operates at 12 MHz and has an array dimension of 50×5 mm. A Bscan having the following characteristics was used: depth of image 40mm, gain 55, dynamic range A, post processing 2, power 100, sharp 0,frame average High, reject 0.

[0122] In an exemplary embodiment, two points, C and D, are used todetermine points A and B which determine the slope of line 332.

[0123] The dimension of the slope is in brightness levels/(number ofpixels), which is approximately equal to brightness/mm. Due tovariations in taking the images, calibration, etc., the brightnessvalues and slopes can be expected to be correct to within a few percent.Point C is determined by tang the minimum brightness of cartilageportion 304 of graph 300, and in this example, corresponds to a value of37 along the Y-axis. Point B is determined by the first point followingpoint C that has a brightness of 110% of value C.

[0124] Point D is the Maximum brightness of soft tissue portion 306, inthis example, it has a value of 65 on the Y axis. Point A is determinedby taking the first point with a brightness value of 90% of point D andhas a value of 33 on the X-axis in this example. When using otherparameters to calculate such parameters as the CST, the formula ischanged to reflect these parameters.

[0125] The grading obtained from Eq. 1 results in a number usuallybetween 0 to 6 where values close to 0 indicate that the cartilage ishealthy and values close to 6 indicate that the cartilage is unhealthy.A value of 6 on the ultrasound scale, for instance, corresponds to avalue of “4” in the MRI parameters This grading allows the compilationof multiple measurements into a single quantitative value so thatcondition of a joint graded in this fashion can be easily ascertained bya caregiver.

[0126] Alternatively or additionally gradings obtained by X-ray(Kellgren), CT or clinical indices (WOMAC) can serve as the goldenstandards to which the parameters obtained using the ultrasound imageshould be correlated to.

Further Quantitative Measurement of Cartilage

[0127]FIG. 4, illustrates gathering quantitative measurements on a joint400 using a single probe 436 that both transmits and receives data.Alternatively or additionally, two probes, 436 and 434 can be used in analternative method described below. The quantitative measurements ofjoint 400 are specific for evaluating or indicating specific diseasestates as will be explained further on.

[0128] In examination of cartilage 404, bones, 402 and 408 are flexed atapproximately 100 degrees to give a relatively unobstructed examinationof cartilage 404. The obtained ultrasound images are processed to givethe measures mentioned above.

[0129] Alternatively or additionally, a knee joint 100 can be placed inthe fully extended position. Such a position allows a smaller portion ofcartilage 404 to be examined, but a joint capsule 412, that surroundsjoint, 404, is in a relaxed position and joint fluid 414 within jointcapsule 412, can be better visualized by probe 436.

[0130] Alternatively or additionally, joint 400 can be placed in avariety of degrees of extension to view other joint structures as willbe demonstrated below. Alternatively or additionally, joint 400 can beviewed during motion, on or off weight bearing, or during performance ofspecific types of activity, as will be described below.

[0131] In an exemplary method, ultrasound probes 436 and 434 areattached to a gantry that moves at a fixed rate in relation to the jointsurface. This generates an image or values that can be fixed in positioneither relative to the cartilage boundaries or relative to each other.By way of example, cartilage 404 is divided into a grid 438. Grid 438has been divided into transverse sectors 550, 552, 554, 556, 558 and 560and longitudinal sectors A-H. These are one centimeter in square area.

[0132] In an exemplary embodiment of the present invention cartilage 404is evaluated for pits. By way of example, such evaluation isaccomplished using the CSB method described above. Based on this,specific sectors are targeted for further study. In an exemplaryembodiment, data is compiled from sectors that have pits. For example,such data is compiled from a sector 554E, which has 4 pits, a sector560E that has 2 pits, and a sector 560F that has one pit.

Cartilage Thickness Measurement

[0133] In an exemplary embodiment of the present invention, averagecartilage thickness (CT) in sectors with pits is measured. By way ofexample, sector 554E has a CT of 1.2 millimeters, sector 560E has a CTof 1.3 millimeters and section 560F has a CT of 1.4 millimeters.Cartilage from a sector without pitting, such as a sector 554D ismeasured for CT and used as a basis of comparison. Sector 554E forexample has a CT of 2.2 millimeters.

[0134] Additionally or alternatively, quantitative measurements takenwith various methods are correlated for each defined ROI portion. Forexample the CSB method can be correlated with the histogram statisticmethod and conveys information on several aspects of joint structurequality in a value.

Square Area Cartilage Defect Measurement

[0135] In an exemplary embodiment of the present invention, othermeasurements are acquired from the cartilage, such as the square area ofpits (PA) per sector. By way of example, sector 554E has a PA of 0.85square millimeters, 560E has a PA of 1.1 square millimeters and 560F hasa PA of 1.35 square millimeters.

Average Depth Cartilage Defect Measurement

[0136] In an exemplary embodiment of the present invention, the AverageCartilage Pit depth (CPD) is measured. Sector 554E has a CPD of 0.6millimeters, sector 560E has a CPD of 0.6 millimeters and sector 560Fhas a CPD of 1.3 millimeters. By utilizing different collection methods,the accuracy of the measurements can be increased. For instance, byusing invasive probes, such as needles with a small diameter, or byincreasing the frequency, the accuracy can be increased.

[0137] In an exemplary embodiment of the present invention, thisinformation is compiled into a database chart including FIG. 5A that isa reference grid 502 and FIG. 5B that is a table 530 of quantitativemeasurements. A key 532, FIG. 5C, shows reference values of table 530.

[0138] By way of example, table 530 is shown with the data from sector554 E, sector 558D sector 560E and 560F. Data from FIG. 4 is used tocompute further quantitative ultrasound joint measurements as describedbelow.

Cubic Volume Cartilage Defect Measurement

[0139] In an exemplary embodiment of the present invention, the squarearea of pits (PA) in each sector and the Average Cartilage Pit Depth(CPD) are used to give the Cubic Volume of Pitting (CPV) in each sector.By way of example, Cubic Volume of Pits (CPV) in row 560 is 0.560 cubicmillimeters. CPV of row 222 is zero as this sector contains no pits. CPVof row 524 is 0.682 cubic millimeters and CPV of row 526 is 0.65 cubicmillimeters.

Quantitative Value for Cartilage Volume Measurement

[0140] Total Cubic Cartilage volume (TCV) comprises the cartilage area,which in this example is 100 millimeters, multiplied by the CartilageThickness (CT) in millimeters.

[0141] In an exemplary embodiment of the present invention, the CPV issubtracted from the TCV to give the Cartilage Cubic Volume (CCV) 534.This is an example of a quantitative measurement that summarizes anumber of values for a given sector of the cartilage surface 404.

Significant Quantitative Cartilage Values

[0142] Alternatively or additionally, the data is expressed as an arrayof two or more numbers, such as CCV and P (the number of pits) (CCV, P),to give information about the cartilage volume and number of pits in agiven sector. For example (CCV, P) for sector 554E is (121.48 , 4), forsector 558D (CCV, P) is (442, 0), (CCV, P) for sector 560E is (135.58,2) and for sector 560F (CCV, P) is (138.35, 1). By way of example,cartilage donor sites require a CCV above 140 cubic millimeters and a Pof 0 to 1.

[0143] Alternatively or additionally, the data is collected from allsectors and expressed as an average value of sectors. In an exemplaryembodiment, the average CCV of all pitted sectors is 131.87 cubicmillimeters while the average number of pits is 1.75, giving (CCV , P)AV. of (131.87, 1.75) in pitted sectors 304E, 560E and 560F.

[0144] By way of example, such information provides a basis for furtherexamination of particular sectors. In an exemplary embodiment of thepresent invention, sectors with low CCV 534 are targeted for measurementof adjacent cartilage surfaces. Adjacent cartilage surfaces are measuredto determine the extent of a particular condition. By way of example, intraumatic damage to joint cartilage, sectors adjacent to a sector withextensive damage are examined to determine the extent, shape and depthof the resultant damage.

Quantitative Measurement for Cartilage Grafting

[0145] In an exemplary embodiment of the present invention, informationabout the extent of traumatic damage and/or arthritic damage to jointcartilage provide a picture that guides a surgeon in cartilage graftingduring joint reconstruction.

[0146] By way of example, the three areas with pitting 554E, 560E and560F indicate a possible need for cartilage replacement. Sector 558C andother sectors with similar measurements of thicker cartilage withoutpits, indicate that such sectors are suitable as cartilage donor sites.

Other Joint Structure Quantitative Measurement

[0147] When cyst extent is measured in such disease states ashyperuricemia, smaller areas, such as five millimeters square, can beassessed using broadband ultrasound attenuation, for example, with lowerattenuation of the signal indicating a possible cyst.

[0148] In an exemplary embodiment of the present invention, additionaljoint aspects are measured and quantified. By way of example, density orresilience of joint capsule, ligaments, tendons and other soft tissuestructures that make up the joint are measured.

Database Analysis of Quantitative Measurement

[0149] In an exemplary embodiment two or more quantitative ultrasoundjoint measurements are compiled into a database according to personalparameters such as age, sex or ethnic group, athletic or exerciseregimen, or systemic parameters such as genetic or traumatic jointdisease states. Additionally or alternatively, two or more quantitativeultrasound are compiled into a database on the basis of a qualitativeassociation with measurements from, for example, X-ray, MRI, or isotopeuptake. Additionally or alternatively, two or more quantitativemeasurements are combined with each other to provide a qualitativeparameter of joint state and entered into a database.

[0150] In an exemplary embodiment, a database containing quantitativeand qualitative joint information that are correlated with a variety ofpersonal, systemic and qualitative parameters is used to provide aqualitative characterization of one or more joint measures acquired froma subject. In an exemplary embodiment, such analysis of information isprovided on a visual display or in a printed readout of informationwhere, for example, the data is organized into three dimensional modelof said joint.

Correlative Database Update

[0151] A method for continued database update and enhancement fromacquired data is provided so that the database is continually expandingthe scope of correlative information to which newly acquired data iscompared. Such update and enhancement provides for establishing acorrelation between acquired quantitative measures and quantitative,qualitative measures that are organized and correlated according to avariety of quantitative and qualitative measures and personalparameters. In an exemplary embodiment, the establishment of acorrelation of database information with acquired quantitative measuresutilizes associative formulae that are contained in processing softwareof the database. Additionally or alternatively, input of acquiredinformation is accomplished through a neural network whereby a newcorrelation of parameters and quantitative measures are established toprovide new values, qualitative correlation, or measurement standards tobe used for analyzing further values that are acquired. Such new valuesare then, for example, used in the analysis of all further quantitativemeasures in the database.

Quantitative Measurement Database of Athletic Activity

[0152] In an exemplary embodiment of the present invention the databaseis organized based on individuals with common activity interests. Andexample of common activity interest is groups of swimmers, skiers ormarathon runners. In an exemplary embodiment of the present inventionthe data is organized according to intensity of common activity and suchfactors as health status and diet.

[0153] In an exemplary embodiment of the present invention, the databaseof quantitative ultrasound joint information correlates jointmeasurements from athletes with any of a number of joint characteristicssuch as cartilage, capsule thickness, and other aspects of the kneejoint.

Joint Position and Quantitative Measurement

[0154] Joint pathology may only present as a symptom in a certainposition, such as pain of the elbow when the hand is maximally rotatedon the arm or at a specific point during range of motion. By measuringmotion and contact area, a number of quantitative measurements can bederived. In an exemplary embodiment, the ultrasound database includesdata that is acquired from measurements of joint structures with thejoints in a variety of positions such as flexion, extension, supination,eversion, on weight bearing, off weight bearing.

[0155] In an exemplary embodiment of the present invention, quantitativeultrasound joint measurements are acquired during and/or followingregimens such as walking, running and/or aerobic exercise. Such databaseinformation, for instance, provides guidance to training athletes. Bycomparing joint movement of a single athlete to that database,potentially damaging joint positions are averted or splinted, preventingjoint damage during athletic competition.

Quantitative Measurement and Treatment Regimen

[0156] An embodiment of the present invention correlates the ultrasounddatabase with pathologic conditions such as joint pain, inflammation,imbalance and trauma.

[0157] By way of example, the database includes quantitative data ontreatment regimen in joint inflammation, healing time, and/or treatmentsequella of athletes. The database correlates a treatment regimen suchas local or systemic medication, orthotic braces and/or physical therapyto a specific athletic activity.

[0158] Additionally or alternatively, the database correlatesquantitative ultrasound measurements in genetic joint diseases withdisease-related blood titers. The correlative database is used inpredicting disease course and/or giving treatment to diseases such asrheumatoid and psoriatic arthritis. Additionally or alternativelyquantitative ultrasound joint measurements are used in detection andtreatment of joint changes in genetic-related based joint diseases.

Global Quantitative Measurement

[0159] In an exemplary embodiment of the present invention, a globalultrasound measurement, such as CCV, is made of an entire joint toassess treatment in cases of worn or damaged cartilage. Such measurementdirects the caregiver in cartilage replacement, such as whether toreplace a single condyle, or the entire knee.

Through Probe for Collection of Data

[0160]FIG. 4 illustrates a “through” method of collection of data inwhich an ultrasound probe 434 is an emitter of ultrasound waves and aprobe 436 is a receiver of ultrasound waves with ultrasound wavestraveling in a line 440 through a joint 400. Probes 434 and 436 are usedto measure an area of cartilage 404 of a knee joint 400 or otherstructures. Optionally, the two probes are coupled to each other, forexample, using a gantry (not shown) to fix their relative positionsand/or orientations.

[0161] In the through method, typically, the frequency emission is inthe range of 200 kHz to 10 MHz. The through method frequency rangediffers from that of the Echo/Imaging method where the range can be,typically, 5 MHz to 25 MHz because the Echo/Imaging method is used todetermine spatial structure, requiring more precise resolution. Thethrough method does not necessarily image the joint structure and uses alower frequency to acquire data from greater tissue depth with highersignal to noise. However, higher or lower frequencies may be used ineither method.

[0162] In one embodiment of the through method, when the structuremeasured is covered by a thick layer of soft tissue, a frequency closerto 200 kHz is used, as a higher frequency attenuates while going throughseveral centimeters of tissue. Alternatively, when the structure beingmeasured is more superficial, and greater clarity of microstructure isdesired, a higher ultrasound frequency, such as 10 MHz or even 50 MHz orhigher, may be used. The use of far higher frequencies with greaterpenetration, or lower frequencies with greater tissue clarity, may befacilitated by suitable probe design.

[0163] In using this method in a knee joint 412, probes 436 and 434 areheld on the sides of the knee when the leg is fully extended.Alternatively, as shown, probes 436 and 434 are held at either side ofthe joint anterior or at the sub patella notches, while the knee isflexed at 90 degrees. The data is analyzed based on spectral analysis(frequency domain) and/or temporal analysis (time domain) of thereceived ultrasound signal, to characterize a biologic tissue.

[0164] Osteophytes, for example, filter out high frequencies. Whencomparing the spectrum of a signal obtained from a healthy joint and anosteoarthritic joint, the healthy joint spectrum includes higherfrequencies. Changes in signal frequency characteristics may establishthe existence, size and/or quantity of osteophytes.

Echo Method for Collection of Data

[0165] The Echo method, shown in FIG. 1, uses a single probe such astraducer 436 operating in a pulse echo mode, where the same probe bothemits a signal and receives the pulse echo. Typically the probe emitsultrasound in the range of 5 MHz to 25 MHz. Probe 436 is connected to acontrolling device consisting of a pulse receiver and signal recorder.

[0166] The analysis is based upon time domain and/or frequency domainanalysis of the ultrasound signal. For instance, the cartilage entry andexit echoes are identified and the signal received between the two isanalyzed to ascertain the quality of the cartilage in terms ofhomogeneity versus graininess. Alternatively, a single probe is movedalong the cartilage for joint scanning purposes to map the entire jointwithout producing an image.

Analysis of Alternative Joint Structure

[0167] In an exemplary embodiment, FIG. 6 illustrates quantitativeultrasound measurement of a plurality of different joint structures witha probe 636. Backscatter of ultrasound signal can be used to measure thepresence of an inclusion body 642 in collateral ligament 640 and aids inlocation and removal of an inclusion body 642 during surgery.Backscatter of ultrasound signal is described in: Wear, K A, Garra, B S,“Assessment of bone density using ultrasonic backscatter”, UltrasoundMed Biol 1998 Jun; 24(5):689-95.

Alternative Joint-Type Quantitative Measurements

[0168] Alternatively or additionally probe 636 measures joints that donot contain joint fluid. An example is a joint 600 between fibula 672and tibia 608, that is referred to as a syndesmosis. This jointdisplaces in high fractures of fibula 636. By way of example, probe 636measures disruption between fibula 672 and tibia 608 in a damaged jointby measuring the amount of attenuation of the signal. When thesyndesmosis is disrupted, there is less attenuation of signal and alower frequency absorption. Alternatively, probe 636 can measure otherparameters in this joint or in other syndesmotic joints. For instance,by measuring backscatter, the present and/or amount of bone fragmentscan be assessed. An increase in bone fragments, for example, can causeincreased backscatter of acoustic signal, as described in: Wear K A,Garra B S, “Assessment of bone density using ultrasonic backscatter”,Ultrasound Med Biol 1998 Jun; 24(5):689-95.

[0169] In an exemplary embodiment of the present invention, ultrasoundprobe 636 measures a cyst 682 in a joint structure. By way of example,cyst 682 contains material such as metal debris that has broken offimplanted bone hardware or a tumor such as in a Giant Cell tumor andquantitative ultrasound measurement, for example, can made withBroadband Ultrasound Attenuation or Dispersion of ultrasound signal.

Quantitative Measurements and Blood Data

[0170] In an exemplary embodiment of the present invention, the level ofUric Acid in the blood and/or the period of elevation, are correlatedwith quantitative measurements of uric acid cysts in joint structures.

Cartilage Grafting and Quantitative Measurements

[0171] An exemplary application of the present invention is, as noted,in placing cartilage implants. A cartilage plug 662 shown contains acartilage surface, 664 and a bone portion 666. Typically, cartilage plug662 is cylindrical in structure and acquired from a donor area 668 ofjoint 600 where the cartilage generally does not bear weight and hencecontains fewer pits in its surface. As an example, a recipient area bore680 is made in cartilage 616 to the same depth as the height ofcartilage plug 662 and cartilage plug 662 is placed into recipient bore680

[0172] In an exemplary embodiment, a needle shaped ultrasound probe 634contains an ultrasound transmitter and ultrasound receiver, or a smallarray of transducers and is used for intra-operative joint inspection.Additionally or alternatively, an ultrasound probe can provide a phasedarray or swept beam ultrasound.

Growth Plates and Quantitative Measurements

[0173]FIG. 7 shows an ultrasound probe 780 making quantitativemeasurements of a damaged pediatric bone 770. In an embodiment of thepresent invention this information is correlated with a databasespecific to a subgroup such as growing joints in children.

[0174] Pediatric bone 770 is typical for bones such as the humorus andradius that make up the elbow joint. Pediatric bone 770 contains ametaphysis 784, a growth plate 786 and an epiphysis 788. For instance,the speed of sound in cartilage through growth plate 786 is about 1700meters per second (m/s) while speed of sound in bone, such as throughmetaphysis 784 is about 2000-4500 m/s, depending on probe localizationand age.

[0175] In an exemplary embodiment of the present invention pediatricmeasures, such as quality, width and/or volume of growth plate 786, arecompiled into a database. Abnormal values may indicate a need, forexample, for blood testing of growth hormone levels with the need forsuch tests being signaled, for example, by data processing software, aswill be explained below.

[0176] Pediatric bone 770 has a fracture 790 that extends throughepiphysis 788, growth plate 786 and metaphysis 784 with a fracturefragment 794 that is displaced on bone 770.

[0177] The broadband ultrasound attenuation from area 794 is increaseddue to the presence of ossified bone 794 that has separated from bone770. Additionally or alternatively, by taking measurements radiallyaround bone area 794, fracture 790 is located and its extent isdetermined. For example, acoustic speed of sound will show markedchanges as the signal passes normal to area 790 and through fracture 790while the speed of sound of signal passing parallel to area 790 willappear almost normal. Additionally or alternatively, Dispersion ofacoustic signal from any angle to fracture 790 in area 794, will changerelative to that of a non-fractured area bone.

[0178] In an exemplary embodiment of the present invention, quantitativeultrasound measurements provide information on diagnosis, prognosis, andpreferred therapy in treatment of injury of metaphysis 784, growth plate786 and epiphysis 788. For example, measurements of displaced fragment794 that are correlated with the database provide information as to thenecessity for open surgical reduction of fragment 794 as opposed toclosed manipulation so that fragment 794 heals in the proper position.Post reduction quantitative ultrasound measurements demonstrate theprogress of proper incorporation of fragment 794 into the jointstructures.

Equine Quantitative Measurements

[0179]FIGS. 8A and 8B illustrate two views of a talocrural joint 800 ofa horse, with 802 being a Caudal view and 804 being a Cranial view. Theequine talocrural joint 800 is made up of a Calcaneus 810, a Talus 812,a central tarsus 814, a fourth tarsal 816, a third tarsal 818, a firstand second tarsal bone 820 that is fused, a third metatarsal 822, afourth metatarsal 824 and a second metatarsal 826.

[0180] A probe 830 is positioned directly against the soft tissue 840over Talus 812 of the equine talocrural joint 800 as seen in Caudal view802 and in Cranial view 804, giving information about equine talocruraljoint 800. The equine talocrural joint is highly susceptible toinflammation due to overuse and imbalance. Joint inflammation ischaracterized by changes in the viscosity of joint fluid, presence ofinflammatory cells in the joint fluid and thickening of the jointcapsule, among other symptoms. With increased effusion, the speed ofsound decreases.

[0181] In an exemplary embodiment of the present invention, equinetalocrucal joints are examined for OA and a database is compiled. By wayof example, information obtained and analyzed from such a databaseallows rapid diagnosis of joint inflammation and osteoarthritis and isused to predict, for example, the ability for a racehorse to recoverfrom a given injury, or injury cycle.

A Quantitative Measurement and Analysis Appratus

[0182]FIG. 9 is a block diagram 900 showing an embodiment of acomputational system used in quantitative joint structure measurements.

[0183] In an exemplary embodiment of the present invention, data iscollected in an ultrasound measurement collector 902. By way of example,ultrasound probes 434 and 436 make measurements of pitting in an area ofcartilage as part of measurement collector 902.

[0184] In an exemplary embodiment of the present invention, a feedbackfilter 904 processes the information. Feedback filter 904 data isprocessed to determine the quality of the ultrasound signal and adjustschanges in such ultrasound parameters such as signal amplitudeAlternatively or additionally, feedback filter 904 requests analternative ultrasound collection technique that is appropriate forgenerating specific joint data. As an example, feedback filter 902 mayrequest region of interest imaging data with the echo transducer methodafter receiving speed of sound data compiled with a through traducermethod, providing necessary additional information.

[0185] In an exemplary embodiment of the present invention, measurementsare sent to a quantification system 910 that suggests additionalquantitative ultrasound measurements based upon the evolving picture ofthe data in comparison to database quantitative measurements.

[0186] In an exemplary optional embodiment of the present inventionquantitative data is processed in a population comparison system 920where information is analyzed according to population data such as thesubject's age, weight, and/or ethnic character. Alternatively oradditionally, data is analyzed by the database according to the type andamount of sports activities the subject is engaged in.

[0187] Optionally data 910 is processed by a genetic screening system922 genetic tendencies to develop a joint disease such as RheumatoidArthritis are determined. Optionally data 910 is sent to a personal datasystem 924 where the data is compared to prior measurements acquired onthe same subject such as prior measurements of cartilage pitting.

[0188] A confirmatory input system 930 correlates the data, according toa software processing program, comparing it to existing data. System 930also may analyze the data to determine further measurements that need tobe acquired such as data input from a new region of interest.Optionally, confirmatory input system 930 suggests one or more bloodtests that need to be performed such as the need for blood uric acidtesting in the presence of uric acid cysts in the joint.

[0189] In an exemplary embodiment of the present invention, theinformation from all additional testing is entered into confirmatoryinput 930 where it is processed and sent to a database entry system 936where the data is entered order to augment an existing database.

[0190] Confirmatory input 930 generates a display 912. Typically, thedisplay displays inter alia an image similar to wire frame 544, a table530 and/or a key 532 combining information about the joint, populationcomparison and/or disease state noted above. Alternatively oradditionally, the data is placed within a grid 544, with the data ofeach sector being displayed in numbers contained within the sector.Optionally, each sector contains a large amount of data that can beviewed when the operator chooses a particular sector. As an example,grid 544 is shown on a touch-sensitive computer screen and each sectorenlarges on screen when touched with a pointer or the operator's finger.The information provided in this grid system gives indication about thestructure based upon quantitative measurements. Optionally, it providesqualitative analysis, such as indication of disease, severity ofsymptoms and/or prognosis.

[0191] Optionally, display 912 provides a chart such as chart 530. Sucha chart provides a summary list of significant findings and/or anindication of disease. The information is shown on display 912 andprinted by printout system 934.

[0192] While the invention has been described with respect to limitednumber of embodiments, it will be appreciated that many variations,modifications and other applications of the invention may be made. Also,elements from different embodiments may be provide din a singleembodiment or a plurality of elements may be provided as a singleelements may be used. Any and all such variations and modifications, aswell as others that may become apparent to those skilled in the art areintended to be included within the scope of the invention, as defined bythe appended claims.

[0193] The terms “include”, “comprise” and “have” and their conjugatesas used herein mean “including but not necessarily limited to.”

[0194] It will be appreciated by a person skilled in the art that thepresent invention is not limited by what has thus far been described.Rather, the scope of the present invention is limited only by thefollowing claims.

1-66. (Cancelled)
 67. A method of assessing condition of a skeletaljoint comprising cartilage contiguous with bone and soft tissue in thejoint, the method comprising: generating an ultrasound image comprisingimage pixels of the joint; generating a measure of the sharpness of aninterface between the cartilage and soft tissue and/or bone responsiveto the image; and using the sharpness measure to assess condition of thejoint.
 68. A method according to claim 67 and comprising generating ameasure of the brightness of a region of the image and using thebrightness measure to assess condition of the joint.
 69. A methodaccording to claim 67 wherein generating a sharpness measure comprises:defining a plurality of substantially parallel lines in the image;determining a value for brightness for each line responsive tobrightness of pixels along the line; and using the determined brightnessvalues to generate the measure.
 70. A method according to claim 69wherein the brightness value for a line is an average of brightness of aplurality of pixels along the line.
 71. A method according to claim 70wherein at least some of the lines are substantially parallel to theinterface.
 72. A method according to claim 71 wherein generating themeasure of sharpness comprises determining a rate of change of linebrightness as a function of line location for line locations associatedwith the neighborhood of the interface and using the rate of change togenerate the sharpness measure.
 73. A method according to claim 72 anddetermining that the sharpness measure indicates that the interface isrelatively sharp if the rate of change is relatively high.
 74. A methodaccording to claim 72 and determining that the sharpness measureindicates that the interface is not relatively sharp if the rate ofchange is relatively low.
 75. A method according to claim 67 andcomprising determining that tissue adjoining the interface is relativelyhealthy if the sharpness measure indicates that the interface isrelatively sharp.
 76. A method according to claim 67 and comprisingdetermining that tissue adjoining the interface is damaged if thesharpness measure indicates that the interface is not relatively sharp.77. A method according to claim 68 wherein the brightness measure isdetermined for a region of cartilage.
 78. A method according to claim 77and determining that the cartilage is relatively healthy if thebrightness measure indicates that the region is relatively dark.
 79. Amethod according to claim 77 and determining that the cartilage isdamaged if the brightness measure indicates that the region isrelatively bright.
 80. A method according to claim 68 wherein thebrightness measure is determined for a region of bone.
 81. A methodaccording to claim 80 and determining that the bone is relativelyhealthy if the brightness measure indicates that the region isrelatively bright.
 82. A method according to claim 80 and determiningthat the bone is damaged if the brightness measure indicates that theregion brightness is relatively low.
 83. A method according to claim 67wherein the image is a B-scan image.
 84. A method of assessing conditionof a skeletal joint comprising cartilage contiguous with bone and softtissue in the joint, the method comprising: generating an ultrasoundimage comprising image pixels of the joint; defining a plurality ofsubstantially parallel lines in the image; determining a value forbrightness for each line responsive to brightness of pixels along theline; and using the determined brightness values to determine conditionof the joint.
 85. A method according to claim 84 wherein the brightnessfor each line is an average brightness of a plurality of pixels alongthe line.
 86. A method according to claim 84 wherein the image is aB-scan image.
 87. A method according to claim 84 wherein usingbrightness comprises determining whether an anomalous brightness existsin the image.
 88. A method according to claim 87 wherein the anomalousbrightness comprises an anomalously high brightness.
 89. A methodaccording to claim 88 and determining that the cartilage is damaged ifthe anomalously high brightness is associated with locations in thecartilage.
 90. A method according to claim 87 wherein the anomalousbrightness comprises an anomalously low brightness.
 91. A methodaccording to claim 90 and determining that bone is damaged if theanomalously low brightness is associated with locations in the bone. 92.A method according to claim 87 wherein using brightness comprisesdetermining whether an anomalous brightness extends over a relativelylarge number of lines.
 93. A method according to claim 92 anddetermining that the cartilage is damaged if the anomalous brightnessextends over a relatively large number of line locations.
 94. A methodaccording to claim 84 wherein using brightness comprises determining anaverage of the brightness values for a region of the joint through whicha plurality of the lines pass and using the average to assess jointcondition.
 95. A method according to claim 94 wherein the regioncomprises a region cartilage in the joint.
 96. A method according toclaim 95 and determining that the cartilage is damaged if the averagebrightness is relatively high.
 97. A method according to claim 96wherein the region comprises a region of bone in the joint.
 98. A methodaccording to claim 97 and determining that the bone is damaged if theaverage brightness is relatively low.
 99. A method according to claim 84wherein at least some of the lines are substantially parallel to aninterface between the cartilage and bone and/or soft tissue in thejoint.
 100. A method according to claim 99 wherein using brightnesscomprises determining a rate of change of brightness as a function ofline location.
 101. A method according to claim 100 wherein determiningthe rate of change comprises determining the rate of change for linelocations associated with the neighborhood of an interface.
 102. Amethod according to claim 101 and determining that tissue adjoining theinterface is relatively healthy if the rate of change is relativelyhigh.
 103. A method according to claim 101 and determining that tissueadjoining the interface is damaged if the rate of change is relativelylow.
 104. A method according to claim 101 and determining that tissueadjoining the interface is damaged if the rate of change is erratic.105. A method according to claim 84 wherein using brightness comprisesusing a minimum value for brightness for line locations associated withthe cartilage.
 106. A method according to claim 84 wherein usingbrightness comprises using a maximum value for brightness for linelocations associated with the bone.
 107. A method according to claim 84wherein using brightness comprises generating a value responsive to arate of change in brightness as a function of line locations associatedwith a soft-tissue cartilage interface, a minimum value for brightnessfor line locations associated with the cartilage and a maximum value ofbrightness for line locations associated with the bone.
 108. A methodaccording to claim 107 wherein the function is a linear function of therate of change, minimum and maximum brightness values.
 109. A methodaccording to claim 84 wherein the joint is a human joint.
 110. A methodaccording to claim 84 wherein the joint is an equine joint.
 111. Amethod according to claim 68 and comprising using a value of a functionof the sharpness measure of at least one interface and a measure ofbrightness of at least one region to assess joint condition.
 112. Amethod according to claim 108 wherein the function is a linear function.113. A method according to claim 68 wherein the joint is a human joint.114. A method according to claim 68 wherein the joint is an equinejoint.